Seminarium: Worldsheet methods for interactions on curved backgrounds

The study of string theory on curved background fields is notoriously difficult: quantum consistency of the worldsheet CFT imposes an infinite tower of constraints on the background fields, and calculations which were straightforward for flat backgrounds (e.g., writing vertex operators, computing 3-point functions) are practically impossible. I will discuss how certain chiral, constrained worldsheet theories (known as 'ambitwistor strings') describe QFT degrees of freedom directly and avoid many of the difficulties associated with ordinary strings on curved backgrounds. This provides a new tool for studying perturbation theory on curved backgrounds from a worldsheet perspective. As an example, we will consider certain plane wave backgrounds, and see that the worldsheet theory can be quantized, vertex operators written down, and 3-point functions computed explicitly.